Some peculiarities of activity for comets with orbits on 2 - 5 AU E. Yu. Musiichuk1, S. A. Borysenko2, 1 Taras Shevchenko National University of Kyiv, Glushkova ave., 4, 03127, Kyiv, Ukraine 2Main astronomical observatory, National Academy of Sciences, 27 Akad. Zabolotnoho Str., 03143, Kyiv, Ukraine [email protected] Periodic comets of different dynamical groups with orbits at 2 - 5 AU still occasionally active. The observed dust activity of such objects can be connected with processes of water ice sublimation (MBCs) or crystallization of amorphous water ice (QHCs) as well as with external causes. No connections of cometary flares with cyclic variations of solar activity indexes were found. But some individual solar flares can affect the brightness of comets. Cometary objects in the main asteroid belt have lower statistic of flares than comets at orbits like to quasi-Hilda objects. Key words: Sun: activity, flares; comets: general Introduction Main-belt comets (MBCs) are bodies orbiting within the asteroid belt that have shown comet-like activity during part of their orbit. The first active object in the main-belt was discovered in 1996. About two dozens of main-belt comets (MBCs) were discovered for the last 20 years. Many of them were discovered at outburst [3]. We present heliocentric distribution of cometary flares as a function of heliocentric longitude and heliocentric distance. Also we used the same analysis for some ecliptic [1] and quasi-Hilda comets (QHCs) as a comparison. A quasi- Hilda comet (QHC) is a Jupiter-family comet that interacts strongly with Jupiter and undergoes extended temporary capture by it. These comets are associated with the Hilda asteroid zone in the 3:2 inner mean-motion resonance with Jupiter. Typically, asteroids in this zone have a semimajor axis between 3.70 and 4.20 AU, eccentricities below 0.30, and inclinations of no more than 20 degrees [11]. Usually, comets with orbits at the heliocentric distances more than 2 AU don’t have emissions in their spectrum. Only dust activity can be observed occasionally in the MBCs as well as in the most of QHCs. In this reason, it is interesting to compare the frequency of cometary flares with the indices of the 11-year cyclic activity of the Sun. Some orbital and physical parameters of the selected comets are listed in Table 1. Heliocentric distribution of cometary flares We used data of cometary brightness from on-line databases: Minor Planet Center (minorplanetcenter.net) and Seiichi Yoshida’s database (www.aerith.net) Heliocentric longitude at the maximum of outburst was calculated using JPL’s HORIZONS system (ssd.jpl.nasa.gov) (Fig.1). We chose only cometary flares with amplitudes 2m and more to avoid variations of brightness caused by rotation or photometric errors. We used data of Solar X-ray fluxes (1 - 8 Å) from SPACE WEATHER PREDICTION CENTER (SWPC)(https://www.swpc.noaa.gov) by results of Geostationary Operational Environmental Satellite sys-tem (GOES). The GOES operated by the United States’ National Oceanic and Atmospheric Administration’s National Environmental Satellite, Data, and Information Service division, supports weather fore-casting, severe storm tracking, and meteorology research. Spacecraft and ground-based elements of the system are work together to provide a continuous stream of environmental data (http://www.polarlicht-vorhersage.de/goes_archive). Large solar X-ray flares can change the Earth’s ionosphere, which blocks high-frequency (HF) radio transmissions on the sunlit side of the Earth. Solar flares are also associated with Coronal Mass Ejections (CMEs) which can ultimately lead to geomagnetic storms. SWPC sends out space weather alerts at the M5 level. Some large flares are accompanied by strong radio bursts that may interfere with other radio 1 Advances in Astronomy and Space Physics, 9, 3-7 (2019) Table 1: Orbital and physical parameters of selected comets ◦ T Comet q (AU) a (AU) e i ( ) P (yr) J H10(nucl) Type 47P/Ashbrook – Jackson 2.82 4.13 0.32 13.03 8.38 2.907 13.6 JFC 65P/Gunn 2.91 3.89 0.25 9.18 7.67 2.999 12.0 QHC 74P/Smirnova – Chernyh 3.54 4.16 0.15 6.65 8.49 3.007 12.1 QHC 91P/Russell 3 2.61 3.89 0.33 14.09 7.69 2.920 – JFC 116P/Wild 4 2.19 3.49 0.37 3.61 6.51 3.009 13.0 QHC 117P/Helin – Roman – Alu 1 3.06 4.10 0.25 8.70 8.29 2.967 11.4 QHC 129P/Shoemaker – Levy 3.91 4.29 0.09 3.44 8.89 3.019 – QHC 133P/Elst – Pizarro 2.66 3.17 0.16 1.39 5.63 3.183 15.7 MBC 152P/Helin – Lawrence 3.10 4.49 0.31 9.88 9.50 2.900 – JFC 176P/LINEAR 2.58 3.20 0.19 0.23 5.71 3.166 15.2 MBC 180P/NEAT 2.49 3.86 0.36 16.87 7.58 2.889 14.3 JFC 187P/LINEAR 3.88 4.60 0.16 13.59 9.87 2.936 13.9 QHC 202P/Scotti 2.53 3.79 0.33 2.19 7.37 2.982 15.7 QHC 211P/Hill 2.35 3.56 0.34 18.89 6.70 2.934 – QHC 219P/LINEAR 2.37 3.65 0.35 11.53 6.98 2.961 14.9 QHC 232P/Hill 2.98 4.49 0.33 14.63 9.51 2.853 14.5 JFC 238P/Read 2.37 3.17 0.25 1.26 5.63 3.153 17.6 MBC 243P/NEAT 2.45 3.83 0.36 7.64 7.50 2.946 15.0 QHC 244P/Scotti 3.93 4.90 0.20 2.26 10.8 2.963 12.5 QHC 246P/2010 V2 (NEAT) 2.88 4.03 0.29 15.97 8.08 2.914 11.3 QHC 266P/Christensen 2.33 3.53 0.34 3.43 6.64 3.020 – QHC 287P/Christensen 3.05 4.18 0.27 16.30 8.54 2.902 14.8 QHC 288P/(300163) 2.44 3.05 0.20 3.24 5.32 3.204 16.2 MBC 297P/Beshore 2.34 3.45 0.32 10.33 6.40 3.027 13.8 QHC 324P/La Sagra 2.62 3.10 0.15 21.42 5.45 3.100 15.5 MBC 331P/Gibbs 2.88 3.00 0.04 9.74 5.20 3.229 15.4 MBC 340P/Boattini 3.06 4.25 0.28 2.08 8.76 2.959 14.7 QHC 345P/LINEAR 3.16 4.05 0.22 2.72 8.14 3.005 15.2 QHC 348P/PANSTARRS 2.21 3.17 0.30 17.57 5.64 3.061 18.0 MBC 354P/LINEAR 2.00 2.29 0.12 5.25 3.47 3.583 – MBC 358P/PANSTARRS 2.40 3.15 0.24 11.06 5.59 3.135 17.2 MBC P/1999 XN120 (CATALINA) 3.30 4.18 0.21 5.03 8.55 2.990 13.7 QHC P/2010 H2 (Vales) 3.10 3.85 0.20 14.27 7.55 2.987 – QHC P/2013 R3 (Catalina – PANSTARRS) 2.21 3.04 0.27 0.90 5.29 3.184 16.0 MBC P/2015 F1 (PANSTARRS) 2.54 3.52 0.28 2.80 6.62 3.055 – QHC frequencies and cause problems for satellite communication and radio navigation (GPS). The intensive solar X-rays also can be reason of cometary X-ray emission [9]. Distribution of flares for the main-belt comets are strongly inhomogeneous (Fig. 1 (left)). It is not easy to explain this only by law statistical sampling. Most of outbursts occurred for comets at heliocentric ecliptic longitudes 0 – 60 degrees. All flares in this zone are located along of some arc, which can be an arc of hypothetically orbit of meteor stream. Such stream can not be observable at the Earth due to high eccentricity of the hypothetical orbit (e > 0.5) and perihelion distance q > 1 AU with low inclination (i < 10). It is not clear is the power of meteor stream sufficient to activate comet and increase its brightness. Probably, only concentration of big fragments in the central part of such hypothetical stream can have possibility to disturb dust layer on surface of the main-belt object [2]. For quasi-Hilda comets and some Jupiter-family comets with close orbits we have more homogeneous distribution of flares with good statistic (Fig. 1 (right)). Time intervals of flares between GOES registrations and observations of cometary activity in most cases less than 20 days for QHCs, and about 10 days for MBCs (Fig. 2). Similar analysis for high-energy proton flux data (> 10 MeV) show some smaller number of connected cometary flares. In this case, time interval of "cometary reaction" is only about few days (Fig. 3). 2 Advances in Astronomy and Space Physics, 9, 3-7 (2019) Fig. 1: Heliocentric distribution of cometary flares for MBCs (left) and QHCs (right) over the past 20 years. Fig. 2: Mutual heliocentric distribution of registered solar X-ray flares and cometary flares for MBCs (left) and QHCs (right). (Cometary flares, which can be connected with the solar flares, are signed by the dashed line). For QHCs only about half of flares can be explained by solar activity, but only several for MBCs (Fig. 2). In any case, the analysis of these statistical distributions requires more observational data. Correlations of cometary flares with solar activity We use values indexes of solar activity for the last 20 years to determinate of their correlation with flares for different dynamical groups of comets: SSN – solar spots number; F10.7 – radioflux on the wavelength 10.7 cm; Lα – ultraviolet flux of hydrogen line; Hα – infrared flux of hydrogen line.